MachSchnell

Perhaps the assessment that the 'high' and 'low' levels become less accurate with higher boost levels or temperatures is appropriate here...maybe the car just runs a little hotter (or the turbo does) and the old 'low' level or 'high' level has to compensate down...

Jon Schepps

Peckster-
By "blow-by" on the head side, I meant that there are areas on the head that show that combustion gasses got past the fire ring. There is no physical damage to the fire rings themselves.

Perhaps YOUR car only loses coolant when the headgasket is bad, but there are certainly other mechanisms that could cause this. I've got two perfectly good head gaskets to prove it. I'm concluding that my head and/or block surfaces are not perfectly flat. More likely the block - that is, the tops of the cylinder walls are not perfectly level with the top of the surrounding block.

Also, anything that causes the temperature to go up sufficiently can raise the pressure in the expansion tank and cause an overflow. I still think an improperly cooled turbo can cause boiling water to enter the exp. tank. And certainly a tank cap with too low a release pressure will allow overflow as well.

Peckster

Right, gases were getting by your head gasket. I was confused because I've never heard that referred to as blow-by.

I understand it might be caused by your block or head, but that's still what nmost people call a head gasket problem. We're saying the same thing.

I sure hope for your sake it isn't the block, that would be expensive to remedy.

I'm outta here.

Jason_86_951

One other thought:
The one time that I experienced this in a extreme (lots of overflow) my cap was a little loose. So if your not able to hold as high as pressure the boiling point is lower. So if you have a slightly leaking radiator (thus lower pressure) this would cause it. The on boost correlation could be attributed to just running hotter and boiling quicker.
This does not explain however the hydrocarbon test results.
Just stiring the pot.
Jason

Songzzz

Sorry to bring this thread back to life... but I figure a crack on the cylinder head at the Intake Port could be the problem.

1. It cannot be detected by compression test.
2. It cannot be detected by HC test, unless intake valve is not sealing well.
3. Problem appears only when under boost.

MySwiss

I run a full 60 to 1 Hi-Fi Garett, without any water cooling. And I experience the same delima.

As soon as I get here under boost, I smell the coolent coming out the overflow. The car always runs very cool (180 ferhenhite), and the, plugs are golden brown. Pressure test (17lbs) are always good (no leaks), and there's no oil in the coolent. The head gasket , was recently replaced, and retorqued with stock head studs, instead of Raceware.

The only conclusion, I can draw, is that the head lifts under pressure, letting the gases enter the coolent, and therefore, pressurizing the cooling system, and overflowing.

Songzzz

Besides O-ringing... what other alternatives?

Songzzz

Besides O-ringing... what other alternatives?

Jason_86_951

Bump

eclou

Wow,

I have the exact same phenomenon since upgrading to a K27/6 and running 18 psi boost. No matter how much coolant I add it always will be at the min mark within a day. I also did the HC in the coolant test on a hot motor and it was negative. Funny that when I open the expansion tank cap the coolant level will rise back to max.

I also have ordered Raceware studs and a WF headgasket, and have also ordered all new radiator hoses and a spare used radiator that I will steam/flush and install.

Eugene

Magown

Just want to add, that my car highly modded car was also loosing coolant last year before I took it off the road. Has anyone found a solution? or is everybody living with it. It ran very cool.

MachSchnell

Again, seems like the only conclusions are:
1) A HUGE number of people have warped or uneven heads (does this really seem likely?)
2) Upping the boost requires either people accept that lower levels are going to be the norm
3) we find a higher pressure rad cap and see if that helps
4) o-ringing the head is a must

I personally am not a big fan of o-ringing as I feel like it's a band aid, and it takes away the 'inexpensive' weak link in the system...I'd rather my HG went than a piston or rod or bearing if I'm detonating, but I'm beginning to fear that the head lifting under boost hypothesis might be an issue, though the proliferation of people experiencing the same problem with racewares makes me feel a little better that this isn't the issue. So again, I ask, has anyone found a higher pressure expansion tank/rad cap for these cars? I'd really like to try this before I do anything more...

Songzzz

For my case, it turns out the head studs were not properly installed . Other possible causes:
1. Improper head stud torqing procedure.
2. Improper installation of Head Gasket
3. Warped Head or Block
4. Weeping Block (look up the recalls and bulletin issued by Porsche)
5. Cracked Head or Block
6. Clogged Radiator or anywhere within the water system.

Pauerman

Just read this post and must add that my '89 has the same coolant loss/overflow issue.

My car would spit coolant out the overflow until it reached the minimum level in the reservoir. After that, it didn't seem to leak any more. The overflow was very obvious at DE events but practically unseen in everyday driving. I've since pulled the head and engine and inspected my head gasket - no obvious defects on both sides of the fire ring.

It'll be interesting to see who'll find a fix - keep this thread going.

Matt H

Besides O-ringing... what other alternatives?

You could weld the head to the block, ala old race cars, but I doubt that would be a good solution here.
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